ST. LOUIS—When Cardinals general manager John Mozeliak set out to boost his team's pitching staff last year, he had an ideal chip in center fielder Colby Rasmus.

Rasmus, a talented, young outfielder, was in need of a fresh start and the Toronto Blue Jays were more than happy to take him in what became a three-team, 11-player trade that brought the Cardinals starter Edwin Jackson and relievers Octavio Dotel and Marc Rzepczynski. The move rightfully was lauded as instrumental in the Cardinals' run to the World Series championship.

When Mozeliak goes shopping this month, he won't have anyone to trade quite like Rasmus. The Cardinals, however, will have an even greater need than a year ago after learning Tuesday that postseason ace Chris Carpenter will undergo season-ending surgery to correct nerve issues in his shoulder.

The Cardinals don't figure to make available any of their top three prospects, starters Shelby Miller and Carlos Martinez and outfielder Oscar Tavares.

But what about minor-league slugger Matt Adams? The 23-year-old lefthanded-hitting first baseman was the franchise's minor league Player of the Year in 2011, and he started strong in a 27-game call-up this season. At 6-foot-3 and 230 pounds, Adams is considered a top power prospect. He has the numbers to prove it: 32 homers last year at Class AA, and a .353/.379/.659 slash line with 13 homers in 45 games this year at Class AAA.

Adams could be expendable, however, because the Cardinals have Allen Craig to take over first base next year. Craig, 27, has been playing first and in the outfield since Lance Berkman suffered a knee injury that required surgery earlier this season. Berkman is expected back shortly after the All-Star break but is on a one-year deal.

In parts of three big-league years, Craig already has proven to be a potent producer at the big-league level. He has hit .300/.358/.552 with 28 homers and 101 RBIs in 159 games, plus he hit four homers last postseason. With Carlos Beltran and Matt Holliday in the corner outfield spots, Craig figures to take over first in 2013, which would leave Adams without a position.

The Cardinals also have another lefty-hitting first baseman in Matt Carpenter, who might not have quite the power that Adams does. When Carpenter came off the disabled list last month, Adams went back to the minors.

The club also could include a utility type such as Skip Schumaker, Tyler Greene or Daniel Descalso to sweeten a deal. Whether or not that would be enough to rent a premier starter such as Zack Greinke or Cole Hamels remains to be seen. Other starters who could be traded before the deadline include Cubs right-hander Matt Garza and Astros lefty Wandy Rodriguez.

Carpenter had been sidelined since early in spring training when he was diagnosed with shoulder fatigue. He took three months to build strength in his shoulder before starting a throwing program. He had made progress but reported weakness after a session 11 days ago that led to seeking a second opinion on exactly what was ailing him. That resulted in a diagnosis of thoracic outlet syndrome.

Carpenter resumed throwing last week but had a session canceled on Monday. Less than 24 hours later, he had decided to undergo a nerve-corrective surgery that requires six months of recovery and rehab. Without the surgery, scheduled for July 19, Carpenter's career likely would have been over.

"I want to pitch again, and this is the way for me to pitch again," Carpenter told reporters Tuesday afternoon. "We tried since spring training to get this going, and every time I tried to come back, unfortunately, it just doesn't allow me to do that."

The Cardinals also have been without lefty starter Jaime Garcia (shoulder) since early June and his return remains indefinite. Plus, they have a bullpen that, like last year, is in need of reinforcements.

Mozeliak had been seeking resolution on Carpenter's status before getting too active on the trade market. No need to wait any longer. Next comes the tough part: figuring out whom to move.